This application claims priority to International Application No. PCT/GB99/04092 which was published on Jun. 29, 2000.
This invention relates to light detection apparatus for determining the location of a body within an area and to an autonomous vehicle, typically a robotic cleaning device, equipped with such light detection apparatus.
An article entitled xe2x80x9cA Compound Eye for a Simple Robotic Insectxe2x80x9d at pages 166-173 of xe2x80x9cRAM-based Neural Networksxe2x80x9d, published 1998, ISBN 981-02-3253-5 describes a machine which has light dependent resistors mounted on the top faces of a truncated icosahedron and which uses a discriminator network to estimate insect position in a room. The discriminator network requires training.
The present invention seeks to provide an improved light detection apparatus which is suitable for use on an autonomous vehicle.
A first aspect of the present invention provides light detection apparatus for determining the location of a body within an area, the apparatus comprising at least two light detecting devices for mounting on the body and capable of receiving light from the environment in which the body is located, the devices being located at respective detecting points which are angularly spaced about a vertical axis, means for supplying information representative of the levels of at least two different light types received at each detecting point, and means for comparing information received from the light detection apparatus with information previously received from the light detection apparatus and stored in a memory so as to identify when the light detected by the light detection apparatus is the same or substantially the same as light previously detected by the light detection apparatus.
A further aspect of the invention provides an autonomous vehicle comprising power operated means for moving the vehicle around an area and a navigation system for identifying the location of the vehicle, the navigation system including the above described light detection apparatus for allowing the vehicle to determine when it has returned to a similar position in the area.
By deriving information representative of at least two different light types received at each detecting position, the apparatus can better discriminate a set of light measurements taken at one position in an area from another position in the area. For example, the overall light level in a particular direction may be the similar, but the relative amounts of the light types making up that similar level may be quite different. The light types can be ambient light and artificial light, such as incandescent light and fluorescent light. The information about different light types can be derived by filtering or by processing the signal received by each light detecting device to derive information about the level of constant (natural light) and time-varying (artificial) light types. The apparatus is particularly useful in an indoor environment where there is usually a mixture of natural and artificial light, the respective light sources being differently positioned within a room.
The light detecting devices can be phototransistors or photodiodes. Alternatively, they can be a CCD array.
Preferably, the points at which light is received are spaced equi-angularly about the vertical axis. This gives the apparatus rotational symmetry.
Preferably, the light detection devices are all supported in a horizontal plane.
Preferably there are at least four, and more preferably, eight light detecting devices.
The light detecting devices can be supported within a housing which can be mounted on an autonomous vehicle.
The autonomous vehicle can be a robotic floor cleaning device, such as a robotic vacuum cleaner.
Preferably the light detection apparatus is supported on an uppermost part of the body with the light detecting devices being supported so that they can receive light over an incident beam angle in a vertical plane extending upwardly from the horizon.
There have been a number of proposals to provide robotic or autonomous vacuum cleaning devices which can clean a floor area without the need for a human user to push or drag the cleaning device along the floor. These generally operate by performing a pattern of coverage of the floor area which is random or reciprocating. Some of these cleaning devices require navigation beacons to be installed in a room to allow the cleaning device to determine its position and to navigate around the floor area.
However, these are undesirable as they require installation in each room where a user wishes to use the cleaning device.
Accordingly, further aspect of the invention provides an autonomous floor cleaning device for cleaning a floor area comprising:
power operated means for moving the vehicle around the floor area and a navigation system for identifying the location of the vehicle and for controlling movement of the cleaning device, wherein the navigation system includes a light detection apparatus comprising:
at least two light detecting devices mounted on the body and capable of receiving light from the environment in which the cleaning device is located, the detecting devices being located at respective light detecting points which are angularly spaced about a vertical axis,
means for supplying information representative of the level of light detected by each light detecting device, and
means for comparing information received from the light detection apparatus with information previously received from the light detection apparatus and stored in a memory so as to identify when the light detected by the light detection apparatus is the same or substantially the same as light previously detected by the light detection apparatus, indicative of the cleaning device returning to a similar position in the area.
The use of the light detection apparatus can avoid the need for navigation beacons. The light detection apparatus is particularly useful where the cleaning device performs a spiralling pattern of coverage of the floor area. After each circuit of the floor area the cleaning device returns to a similar position in the area and this causes the cleaning device to step inwardly (if the spiral is an inward spiral) or outwardly (if the spiral is an outward spiral) by a step distance. The step distance can be fixed, such as one, or substantially one width of the cleaning device, or it can be selectable by a user.
Other aspects of the invention provide a navigation system and software for operating a control processor in a navigation system, which cause an autonomous vehicle to operate in the above way. Further aspects of the invention provide a method of determining position of a body within an area using the light detection apparatus and a method of controlling operation of a cleaning device using information received from the light detection apparatus.